Intercom handset no sound, buzzing or howling: what it means

The sections below go through each in turn.

When the call comes through but the line is silent as you lift the handset, the problem is almost always in the handset itself. Centurion's manual for its wired handset gives two checks:

• The coiled cord. It plugs into the handset and the cradle. A cord that's been pulled, twisted or chewed by a pet loses contact; reseat both plugs and look for damage.
• The hook switch. The small lever or button the handset rests on tells the intercom you've picked up. If it's stuck down, by dirt or a cracked cradle, the system never connects the call. Make sure it moves freely.

If both are fine and other handsets in the house work, the handset has failed and is replaced. If none of them work, the fault is at the gate station or in the cable.

Centurion's checks for a handset that doesn't ring when called are, in order: the supply voltage, the coiled cord, the handset's group setting, and its volume.

The group matters in houses with more than one handset. Centurion's handsets have a selector switch for group A or B, so different gate buttons can ring different handsets: one for the main house, one for a cottage or a flat. A handset switched to the wrong group stays silent while the others ring.

If every handset is silent and the gate station's lights are off, it's power: the supply, its plug point, or the cable to the gate. The general checks are on intercom not working.

A howl during a call is feedback: the gate station's speaker is loud enough for its own microphone to pick it up. Centurion's fix is to turn the entry panel's volume down, and its guide to setting it is simple: turn the volume up until it howls, then back off. The right level is just below the howl.

Centurion also notes that the right volume depends on how many handsets are connected, so a system that was fine with one handset can howl after a second is added, or turn quiet after one is removed. The volume control sits inside the gate station or handset, so if you'd rather not open it, we set it on site.

• A steady buzz or hum from the moment you pick up usually means the power: a failing supply, or a voltage that dips. Centurion's manual lists the supply voltage among its first checks, and an intercom powered from a gate motor's supply can be affected when the motor starts.
• Crackling that comes and goes, especially after rain, points to water: in the gate station, in a cable joint, or where the cable enters the pillar. It often gets worse in wet weather and better in dry.
• On a wireless intercom, crackling and dropping out are usually range. Zartek warns that metal surfaces near the gate unit, and nearby electric fences or cameras, reduce the range.

A gate station that keeps letting water in will crackle again after every storm, and is usually replaced. More on storms and intercoms in gate motor not working after rain or lightning.

A wireless handset, such as Zartek's, works differently from a wired one:

• It runs on a battery. Zartek's handset has a rechargeable lithium battery and lives on a charger stand. A handset that's been off its stand for days may simply be flat; its screen shows a low-battery warning.
• Volume is adjustable during a call, with the volume buttons on the handset. The door chime's loudness, though, is fixed.
• An out-of-range icon appears when the handset can't reach the gate unit, including when the gate unit loses its 12 V power supply. If the icon appears with the handset close to the gate, check the gate unit's power.
• The gate unit is splash- and rain-proof only with its rubber seals and battery cover in place.

Replacing a wireless handset means pairing the new one to the gate unit, which is how they're matched.

Can you replace just the handset? Usually, yes, as long as the new one belongs to the same system:

• Wired systems run on their own signalling; Centurion's handsets, for example, share a two-wire bus, so a handset from another system won't simply plug in.
• Wireless handsets are paired to their gate unit.
• A handset for a flat or cottage is added the same way, on its own group if it should ring separately.
• Moving to video means a screen in place of the handset, and usually a new gate station with a camera.

We don't publish handset wiring diagrams beyond what the makers print, because a wrong connection can damage the system's power supply or the gate motor it opens. Centurion's own manual sets the cable thickness by the distance from the gate, which is worth knowing if you're running a new cable.

We replace handsets for Centurion, BPT, Commax, Zartek and Kocom systems. For handsets from other makers, such as Fermax, Aiphone or GDX, we don't hold the manuals, so we'd need to see the system before saying whether a replacement can be matched.

Tell us what you hear, whether it happens on every handset or one, and whether it's worse after rain. We'll test the handset, the gate station and the cable between them, and replace only what's failed. All our spare parts are genuine, and every repair carries our six-month guarantee on our repairs. Your exact price is set in a free quote before any work starts. No call-out fee when we do the work. If no work is done, a R650 call-out fee applies.

Our intercom work is on intercoms, and what new systems cost on intercom installation cost.